Blade tip to shroud clearance for shrouded fluid turbines

ABSTRACT

Shrouded fluid turbines having features for setting, adjusting or controlling a blade tip-shroud clearance are described. Also described are methods for setting, adjusting or controlling a blade tip-shroud clearance in a shrouded fluid turbine.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and benefit of U.S. Provisional Patent Application No. 61/539,312, filed Sep. 26, 2011, the contents of which are incorporated herein by reference in their entirety.

BACKGROUND

A fluid-driven turbine (e.g., a rotor or impeller) encircled in part or completely by one or more shrouds, ducts, or shells may be described as a shrouded fluid turbine. Examples of shrouded fluid turbines include shrouded wind turbines with wind-driven rotors and shrouded hydro turbines with water-driven rotors. Shrouded fluid turbines that are used to generate power from fluids flowing past the turbine may be described as energy extraction shrouded fluid turbines. In shrouded fluid turbines, the shroud channels the fluid past the rotor, which may increase the efficiency of the turbine. A gap between tips of blades of the rotor and an inner surface of the shroud may be described as a shroud-tip clearance or a shroud-tip gap.

SUMMARY

Example embodiments described herein include, but are not limited to, shrouded fluid turbines with features for controlling, setting or adjusting a shroud-tip gap. Example embodiments described herein also include methods for controlling, setting or adjusting the shroud-tip gap in a shrouded fluid turbine.

In an example embodiment, a shrouded fluid turbine includes a central hub rotatable about a central axis of the shrouded fluid turbine, a blade, a first shroud and an adjustment mechanism. The blade includes a proximal portion with a blade root coupled to the central hub, a distal portion including a blade tip and a mid-portion disposed between the proximal portion and the distal portion. The first shroud has an inner surface in proximity to the blade tip. The adjustment mechanism is configured to adjust a separation between the blade tip and the shroud inner surface by lengthening or shortening a distance between the blade tip and the central hub.

The first shroud may have mixing lobes, which may include high energy mixing lobes and low energy mixing lobes. The shrouded fluid turbine may also include an ejector shroud located downstream from the first shroud. An outlet of the first shroud may extend into an inlet of the ejector shroud.

The adjustment mechanism may radially retract or extend at least a portion of the blade with respect to the central hub. At least a portion of the blade may be extended or retracted telescopically. The adjustment mechanism may displace at least the distal portion and the mid-portion of the blade in a radial direction with respect to the central hub.

The adjustment mechanism may include a coupling between at least the distal portion of the blade and the proximal portion of the blade that permits at least the distal portion of the blade to be rotationally displaced about a non-radial axis relative to the proximal portion of the blade. The coupling may be a hinge coupling the distal portion of the blade and the proximal portion of the blade.

In another example embodiment, a shrouded fluid turbine includes a central hub rotatable about a central axis of the shrouded fluid turbine, a blade, a first shroud and an inflatable bladder. The blade includes a proximal portion with a blade root coupled to the central hub, a distal portion including a blade tip and a mid-portion disposed between the proximal portion and the distal portion. The first shroud has an inner surface in proximity to the blade tip. The inflatable bladder is associated with the inner surface and configured to change a spacing between the blade tip and the inner surface by changing a distance between at least a portion of the inner surface and the central axis upon inflation or upon deflation of at least a portion of the inflatable bladder.

The inflatable bladder may be coupleable to the first shroud. The inflatable bladder may be integral to the first shroud. The inflatable blade may include a plurality of inflatable chambers.

In another example embodiment, a shrouded fluid turbine includes a central hub rotatable about a central axis of the shrouded fluid turbine, a blade, a first shroud and a hinged pitch mechanism. The blade includes a proximal portion with a blade root coupled to the central hub, a distal portion including a blade tip and a mid-portion disposed between the proximal portion and the distal portion. The first shroud has inner surface portions in proximity to the blade tip. The hinged pitch mechanism is configured to lengthen or shorten a distance between at least some of the inner surface portions of the first shroud and the central axis.

The shrouded fluid turbine may further include a control mechanism to control the positions of at least some of the inner surface portions relative to the central axis. The control mechanism may individually control the position of each inner surface portion for a plurality of the inner surface portions.

In one example embodiment, a shrouded fluid turbine includes a central hub rotatable about the central axis, a blade, a first shroud and a clearance control mechanism. The blade includes a proximal portion with a blade root coupled to the central hub, a distal portion including a blade tip and a mid-portion disposed between the proximal portion and the distal portion. The first shroud has inner surface portions in proximity to the blade tip. The clearance control mechanism repels the blade tip from some of the shroud inner surface portions or repels some of the inner surface portions from the blade tip.

The blade tip or some of the shroud inner surface portions may be repelled magnetically. The clearance control mechanism may include a ferromagnetic material disposed in at least one of the proximal portion of the blade and the shroud inner surface portion. The clearance control mechanism may include an electromagnet.

In another example embodiment, an energy extraction shrouded fluid turbine includes a rotor, a first shroud, and an adjustment mechanism. In some embodiments, the energy extraction shrouded fluid turbine includes an ejector shroud downstream from the first shroud. The rotor includes a central hub rotatable about a central axis of the energy extraction shrouded fluid turbine. The rotor also includes a blade with a proximal portion including a blade root coupled to the central hub, a distal portion including a blade tip, and a mid-portion disposed between the proximal portion and the distal portion. The first shroud includes an inner surface in proximity to the blade tip and mixing lobes. The adjustment mechanism is configured to change a distance between the blade tip and the shroud inner surface by lengthening or shortening a distance between at least a portion of the shroud inner surface and the central axis.

The adjustment mechanism may include an inflatable bladder coupled with the shroud inner surface and configured to change a distance between at least a portion of the shroud inner surface and the central axis upon inflation or upon deflation of at least a portion of the inflatable bladder. The adjustment mechanism may include a hinged pitch mechanism.

In one example embodiment, an energy extraction shrouded fluid turbine includes a rotor and a first shroud. The rotor includes a central hub rotatable about a central axis of the energy extraction shrouded fluid turbine. The rotor also includes a blade with a proximal portion including a blade root coupled to the central hub, a distal portion including a blade tip, and a mid-portion disposed between the proximal portion and the distal portion. The first shroud includes an inner surface in proximity to the blade tip and mixing lobes. The inner surface has a radial groove into which the blade tip extends during rotation of the rotor. In one example embodiment, the energy extraction shrouded fluid turbine may also include a second shroud downstream of the first shroud. The second shroud and may be an ejector shroud.

The groove may be at least partially formed through abrasion of the shroud inner surface by the blade tip. The rotor may further include a blade ring coupled to the distal portion of the blade, extending circumferentially about the central axis and extending at least partially into the groove.

In another example embodiment, an energy extraction shrouded fluid turbine includes a rotor and a first shroud. The rotor includes a central hub rotatable about a central axis of the energy extraction shrouded fluid turbine. The rotor also includes a blade with a proximal portion including a blade root coupled to the central hub, a distal portion including a blade tip, and a mid-portion disposed between the proximal portion and the distal portion. The first shroud includes an inner surface in proximity to the blade tip and mixing lobes. The inner surface includes an abradable material having a hardness less than a hardness of the blade tip. The blade tip may occasionally contact the inner surface during rotation of the rotor. The blade tip may include an abrasive material having a hardness greater than a hardness of a mid-portion of the blade. In one example embodiment, the energy extraction shrouded fluid turbine may also include a second shroud downstream of the first shroud. The second shroud and may be an ejector shroud.

In yet another example embodiment, an energy extraction shrouded fluid turbine includes a rotor, a first shroud and may include an ejector shroud located downstream from the first shroud. The rotor includes a central hub rotatable about a central axis of the energy extraction shrouded fluid turbine. The rotor also includes a blade with a proximal portion including a blade root coupled to the central hub, a distal portion including a blade tip, and a mid-portion disposed between the proximal portion and the distal portion. The rotor further includes a blade ring extending circumferentially about the central axis and coupled to the distal portion of the blade. The first shroud includes an inner surface in proximity to the blade ring and mixing lobes. The inner surface of the first shroud may have a radial groove into which the blade ring at least partially extends.

Other example embodiments may incorporate methods. An example embodiment includes a method of adjusting a blade tip-shroud gap spacing in an energy extraction shrouded fluid turbine. The energy extraction shrouded fluid turbine includes a central hub rotatable about a central axis of the energy extraction shrouded fluid turbine, a blade having a blade tip, and a first shroud having an inner surface in proximity to the blade tip. The energy extraction shrouded fluid turbine may further include an ejector shroud, and the first shroud may have mixing lobes.

The method includes sensing a spacing between the blade tip and at least a portion of the inner surface of the first shroud during rotation of the blade about the central axis. The method also includes changing a distance between the blade tip and the central hub in response to the sensed spacing.

Sensing the spacing between the blade tip and the shroud inner surface may include detecting a radial position of the blade tip relative to the central axis or relative to the shroud inner surface. Sensing the spacing between the blade tip and the shroud inner surface may include optically detecting a position of the blade tip relative to the central axis or relative to the shroud inner surface.

Changing a distance between the blade tip and the central hub may include changing the distance between the blade tip and the central hub in real-time during operation of the shrouded fluid turbine. Changing a distance between the blade tip and the central hub may include extending or retracting at least a portion of the blade with respect to the central hub. At least a portion of the blade may be extended or retracted telescopically.

Changing a distance between the blade tip and the central hub includes displacing at least the blade tip and the blade mid-portion in a radial direction with respect to the central hub. Changing a distance between the blade tip and the central hub may include rotating at least the distal portion of the blade relative to the proximal portion of the blade, or relative to the central hub about a non-radial axis.

Another example embodiment is a method of controlling a blade tip-shroud gap spacing in an energy extraction shrouded fluid turbine. The energy extraction shrouded fluid turbine includes a central hub rotatable about a central axis of the energy extraction shrouded fluid turbine, a blade having a blade tip, and a first shroud having an inner surface in proximity to the blade tip. The method includes detecting a spacing between the blade tip and at least a portion of the shroud inner surface during rotation of the blade about the central axis. The method further includes actively controlling a distance between the blade tip and the central hub during rotation of the blade based on the detected spacing. Actively controlling a distance between the blade tip and the central hub during rotation of the blade may include changing the distance between the blade tip and the central hub in real time during operation of the shrouded fluid turbine.

One example embodiment includes a method of adjusting a blade tip-shroud gap spacing in an energy extraction shrouded fluid turbine. The energy extraction shrouded fluid turbine includes a central hub rotatable about a central axis of the energy extraction shrouded fluid turbine, a blade having a blade tip, and a first shroud having an inner surface in proximity to the blade tip. The first shroud may have mixing lobes and the energy extraction shrouded fluid turbine may further include an ejector shroud downstream of the first shroud.

The method includes sensing a spacing between the blade tip and at least a portion of the inner surface of the first shroud during rotation of the blade about the central axis. The method further includes changing a distance between at least a portion of the shroud inner surface and the central axis based on the detected spacing. Changing a distance between at least a portion of the shroud inner surface and the central axis based on the detected spacing may occur during operation of the energy extraction shrouded fluid turbine and during rotation of the blade.

The energy extraction shrouded fluid turbine further includes an inflatable bladder associated with the shroud inner surface. Changing a distance between at least a portion of the shroud inner surface and the central axis may include inflating or deflating at least a portion of the inflatable bladder.

The energy extraction shrouded fluid turbine may further include a hinged pitch mechanism. The distance between a portion of the shroud inner surface and the central axis may be changed using the hinged pitch mechanism.

Another example embodiment includes a method of controlling a blade tip-shroud gap spacing in an energy extraction shrouded fluid turbine. The energy extraction shrouded fluid turbine includes a central hub rotatable about a central axis of the energy extraction shrouded fluid turbine, a blade having a blade tip, a shroud having inner surface portions in proximity to the blade tip, and a clearance control mechanism. The method includes repelling the blade tip from at least some of the shroud inner surface portions or repelling at least some of the shroud inner surface portion from the blade tip during rotation of the blade about the central axis using the clearance control mechanism.

The blade tip may be magnetically repelled from at least some of the shroud inner surface portions or at least some of the inner surface portions may be magnetically repelled from the blade tip. The clearance control mechanism may include ferromagnetic material disposed in at least one of the blade tip and the first shroud. The clearance control mechanism may include an electromagnet.

Another example embodiment includes a method for controlling a blade tip-shroud spacing. The method includes providing an energy extraction shrouded fluid turbine having a rotor and a first shroud. The rotor has a central hub rotatable about a central axis of the energy extraction shrouded fluid turbine and a blade. The blade includes a proximal portion with a blade root coupled to the central hub, a distal portion including a blade tip and a mid-portion disposed between the proximal portion and the distal portion. The first shroud has an inner surface in proximity to the blade tip with the inner surface including an abradable material having a hardness less than a hardness of the blade tip. The method further includes forming a radial groove or trough in the inner surface of the first shroud by at least intermittent contact with the blade tip upon rotation of the blade.

The summary above is provided merely to introduce a selection of concepts that are further described below in the detailed description. The summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the components, processes, and apparatuses disclosed herein may be obtained by reference to the accompanying figures. These figures are intended to illustrate the teachings taught herein and are not intended to show relative sizes and dimensions, or to limit the scope of examples or embodiments. In the drawings, the same numbers are used throughout the drawings to reference like features and components of like function.

FIG. 1 is a right front perspective view of an example embodiment of a shrouded fluid turbine.

FIG. 2 is a side cross-sectional view of the shrouded fluid turbine of FIG. 1.

FIG. 3 is an enlarged cross-sectional view illustrating blade-tip clearance of a shrouded turbine.

FIG. 4 is a perspective view with a detail view of an example shrouded fluid turbine with extendable and retractable rotor blade tips.

FIG. 5 is a side cross-sectional view with a detail view of the example shrouded fluid turbine of FIG. 4.

FIG. 6 is a perspective view with a detail view of an example shrouded fluid turbine with telescopically extendable and retractable rotor blades.

FIG. 7 is a side cross-sectional view with a detail view of the example shrouded fluid turbine of FIG. 6.

FIG. 8 is a side cross-sectional view with a detail view of an example shrouded fluid turbine having blades that can be radially displaced relative to a central hub.

FIG. 9 is a side cross-sectional view with a detail view of a shrouded fluid turbine having hinged blades.

FIG. 10 is a detail view of the shrouded fluid turbine of FIG. 9 showing a blade tip angularly displaced by about 45 degrees.

FIG. 11 is a detail view of the shrouded fluid turbine of FIG. 9 showing a blade tip angularly displaced by about 90 degrees.

FIG. 12 is a side cross-sectional view with a detail view of an example embodiment of a shrouded fluid turbine having a turbine shroud including an inflatable bladder.

FIG. 13 is a side cross-sectional view with a detail view of an example embodiment of a shrouded fluid turbine having a turbine shroud including an inflatable bladder in a cavity of the turbine shroud.

FIG. 14 is a detail cross-sectional view of the shrouded fluid turbine of FIG. 13 showing the inflatable bladder in the cavity with increased inflation.

FIG. 15 is a right front perspective view of an example embodiment of a shrouded fluid turbine with a hinged pitch mechanism.

FIG. 16 is a partial side cross-sectional view of the shrouded fluid turbine of FIG. 15 with hinged shroud portions in a low pitch configuration.

FIG. 17 is a partial side cross-sectional view of the shrouded fluid turbine of FIG. 15 with hinged shroud portions in a high pitch configuration.

FIG. 18 is a right front perspective cutaway view with a detail view of an example embodiment of a shrouded fluid turbine including a blade ring and a turbine shroud having a recess or groove into which the blade ring extends.

FIG. 19 is a side cross-sectional view with a detail view of the shrouded fluid turbine of FIG. 18.

FIG. 20 is a side cross-sectional view with a detail view of a shrouded fluid turbine including a turbine shroud with an abradable inner surface and a recess formed in the abradable inner surface by a blade tip.

FIG. 21 is a right front perspective cutaway view with a detail view of an example embodiment of a shrouded fluid turbine including a magnetic clearance control mechanism.

FIG. 22 is a side cross-sectional view with a detail view of the shrouded fluid turbine of FIG. 21.

FIG. 23 is a right front perspective cutaway view with a detail view of an example embodiment of a shrouded fluid turbine including a blade ring, a turbine shroud having a radial groove, and a magnetic clearance control mechanism.

FIG. 24 is a side cross-sectional view with a detail view of the shrouded fluid turbine of FIG. 23.

FIG. 25 is a right front partially exploded view of a shrouded fluid turbine including a turbine shroud with a high precision front portion and a rear portion including mixing lobes.

FIG. 26 is a side cross-sectional view with a detail view of the shrouded fluid turbine of FIG. 25.

FIG. 27 is a right front perspective view of an example embodiment of a shrouded fluid turbine.

FIG. 28 is a side cross-sectional view of the shrouded fluid turbine of FIG. 27 including an enlarged view of a portion thereof.

FIG. 29 is a flow diagram depicting an example method of adjusting a blade tip-shroud gap spacing of an energy extraction shrouded fluid turbine.

FIG. 30 is a flow diagram depicting another example method of adjusting a blade tip-shroud gap spacing of an energy extraction shrouded fluid turbine.

FIG. 31 is a flow diagram depicting an example method of controlling a blade tip-shroud gap spacing of an energy extraction shrouded fluid turbine.

FIG. 32 is a flow diagram depicting another example method of controlling a blade tip-shroud gap spacing of an energy extraction shrouded fluid turbine.

FIG. 33 is a flow diagram depicting yet another example method of controlling a blade tip-shroud gap spacing of an energy extraction shrouded fluid turbine.

FIG. 34 is a flow diagram depicting an example method of controlling a blade tip-shroud gap spacing.

FIG. 35 is a schematic depicting a system including an array of shrouded fluid turbines.

FIG. 36 schematically depicts a computing environment for controlling one or more shrouded fluid turbines.

DETAILED DESCRIPTION

Example embodiments described herein relate to setting, controlling or adjusting a blade tip-to-shroud clearance in a shrouded fluid turbine. In one embodiment of the present invention, a shrouded fluid turbine may include a turbine shroud and rotor with one or more blades that rotate about a central axis of shrouded fluid turbine. A spacing between an inner surface of the turbine shroud and tips of blades of the rotor is referred to as tip-to-shroud (or shroud-tip) clearance or gap.

In shrouded fluid turbines used for energy extraction (e.g., shrouded wind turbines or shrouded hydro turbines power generation), the efficiency of the shrouded fluid turbine may depend, at least in part, on the shroud-tip gap or clearance. Generally, the smaller the gap between the surface of the shroud and the blade tips, the greater the efficiency of the shrouded fluid turbine. During normal operation, a relatively high efficiency, and a correspondingly small shroud-tip gap, is often desirable. However, decreasing the shroud-tip gap size could increase the risk that a blade tip contacts the shroud inner surface during operation, potentially damaging the rotor, the shroud or both. Thus, during normal operation, it may be desirable to have a shroud-tip gap sufficiently small that efficiency is relatively high, but sufficiently large that a risk that a blade tip contacts the shroud inner surface is acceptably small. For an example shrouded fluid turbine, a gap between the rotor tip and shroud that is equal to 0.5% of the inner radius of the shroud may result in a 2% improvement in efficiency as compared to a gap that is 2% of the inner radius of the shroud.

For energy extraction turbines (e.g., wind turbines or hydro turbines for power generation) excessively high fluid flow conditions (e.g., excessively high winds or high water flow rates) may cause electrical damage due to overloading power generation components or cause mechanical damage due to the rotor rotating at excessive speeds. Under excessively high fluid flow conditions it may be desirable to reduce an efficiency of a shrouded fluid turbine to reduce the risk of overloading electrical components and/or to reduce the risk of exceeding structural and mechanical limits of the fluid turbine. Thus, a larger shroud-tip gap, and a correspondingly lower efficiency, may reduce or prevent damage to a shrouded fluid turbine during excessively high fluid flow conditions.

A shroud-tip clearance or gap may be set or adjusted during initial assembly, construction or installation of a shrouded fluid turbine. The shroud-tip gap may need to be periodically adjusted after assembly, construction or installation to correct for changes in the shroud-tip gap or clearance over time. A shroud-tip clearance may change on a short time scale (e.g., dimensional changes caused by differences in thermal expansion of the rotor and of the shroud, or elastic deformation of components under high or variable ambient fluid flows). A shroud-tip clearance may also change on a long time scale (e.g., non-elastic (creep) deformation of components or dimensional changes due to corrosion).

Example embodiments described herein relate to shrouded fluid turbines having features for controlling, setting or adjusting a shroud-tip gap, as well as methods for controlling, setting or adjusting the shroud-tip gap in a shrouded fluid turbine. The features may be incorporated in a fluid turbine that includes only a first shroud, for example, only a mixer shroud. Likewise, the features may be incorporated in a mixer-ejector turbine that includes a first mixer shroud and an ejector shroud downstream of the first mixer shroud.

To facilitate explanation of the Applicant's contribution to the art of shrouded turbines, FIGS. 1 through 26 are used to describe blade tip-shroud clearance for both shrouded turbines having a single shroud, and for shrouded turbines having more than one shroud. FIGS. 1 through 26 should not be construed as limiting the blade tip-shroud clearance features taught herein to a shrouded turbine with more than one shroud. For example, the embodiments in FIGS. 1 through 26 could be modified to omit the downstream second or additional shroud without changing the blade tip-shroud clearance features of each embodiment.

The blade tip-shroud clearance concepts described and taught herein are equally applicable to shrouded turbines having a single shroud and shrouded turbines having multiple shrouds.

FIGS. 1 through 3 depict an example shrouded fluid turbine 10 in which features for controlling, setting or adjusting a gap spacing between a blade tip and shroud inner surface may be incorporated. The shrouded fluid turbine 10 includes a turbine shroud 20, a nacelle body 16, and a rotor 60 that encircles the nacelle body.

The turbine shroud 20, which also may be identified herein as a mixer shroud, a mixing shroud or a first shroud, includes a front end 22, also known as an inlet end or a leading edge, and a rear end 24, also known as an exhaust end or trailing edge.

In some embodiments the shrouded fluid turbine 10 also includes a second shroud, such as an ejector shroud 40, downstream of the turbine shroud. As illustrated by FIG. 2, the rotor 60, turbine shroud 20, and ejector shroud 40 may be coaxial with each other, (i.e., all share the common central axis 18). The ejector shroud 40, which also may be identified herein as a second shroud, includes a front end 42, also known as an inlet end or leading edge, and a rear end 44, also known as an exhaust end or a trailing edge. As depicted, support members 14 may connect the turbine shroud 20 to the ejector shroud 40.

Throughout this disclosure, the front end (inlet or leading edge) of a first shroud (e.g., a turbine shroud) may be considered the front of a shrouded fluid turbine. For a single shroud embodiment, the rear end (exhaust or trailing edge) of the first shroud (e.g., the turbine shroud) may be considered the rear of the shrouded fluid turbine. For a multi-shroud embodiment, the rear end (exhaust or trailing edge) of the shroud furthest downstream (e.g., the ejector shroud or the second shroud) may be considered the rear of the shrouded fluid turbine. A first component located closer to the front of the shrouded fluid turbine may be considered “upstream” of a second component located closer to the rear of the shrouded fluid turbine (e.g., the turbine shroud upstream of the ejector shroud in a multi-shroud embodiment). The second component may be described as “downstream” of the first component (e.g., the ejector shroud downstream of the turbine shroud in a multi-shroud embodiment).

As illustrated by FIGS. 1 and 2, the rotor 60 includes one or more blades 70 connected to a central hub 62. As used herein, any description of, or reference, to “a blade” or “the blade” refers to some or all blades of a rotor. Although rotor 60 is depicted with four blades 70, in other embodiments, the rotor 30 may include two blades, three blades, four blades or more blades.

The term “rotor” is used herein to refer to any component or assembly in which one or more blades are attached to, or coupled with, a shaft and able to rotate, allowing for the extraction of energy or power from a fluid stream flow that rotates the blade(s). Example rotors include, but are not limited to, a propeller-like rotor, an impeller and a rotor/stator assembly. As understood by one skilled in the art, any type of rotor may be used in conjunction with the turbine shroud in a shrouded fluid turbine of the present disclosure.

Although turbine shroud 20 is shown encircling the rotor 60, in some example embodiments the turbine shroud may only partially encircle the rotor (e.g., the turbine shroud may have gaps, or the rotor may extend beyond the leading edge or trailing edge of the turbine shroud). In some embodiments, the turbine shroud may not encircle the rotor (e.g., the rotor may be positioned in front of the leading edge or past the trailing edge of the turbine shroud).

As illustrated by FIG. 2, the turbine shroud 20 may have the cross-sectional shape of an airfoil with the suction side (i.e., low pressure side) on the interior of the shroud. The rear end 24 of the turbine shroud 20 has mixing lobes that may extend downstream beyond the rotor blades 70. As shown, the mixing lobes may include low energy mixing lobes 26 that extend inward toward the central axis 18, and high energy mixing lobes 28 that extend outward away from the central axis 18. In other words, the rear end 24 of the turbine shroud is shaped to form two different sets of mixing lobes. The turbine shroud 20 may define an opening 27 or channel located between a low energy mixing lobe 26 and a high energy mixing lobe 28 that increases mixing between high and low energy streams. In embodiments with more than one shroud, a rear end 24 of the turbine shroud may extend downstream beyond a front end 24 of the ejector shroud, as shown.

In embodiments with more than one shroud, the shrouded fluid turbine may be described as a mixer-ejector turbine because the low energy mixing lobes 26 and the high energy mixing lobes 28 of the turbine shroud 20 together with the ejector shroud 40 form a mixer-ejector pump. A shrouded fluid turbine incorporating a mixer-ejector pump may more efficiently extract power from a fluid flow than a shrouded fluid turbine that does not include a mixer-ejector pump. As illustrated by FIG. 2, a primary fluid stream 2 is ingested (received) by the turbine shroud 20 and channeled to the rotor 60, which extracts power from the primary fluid stream 2. The ejector shroud 40 of the mixer-ejector pump ingests flow from the primary fluid stream 2 as well as a higher velocity secondary fluid stream 4 that bypasses the turbine shroud 20. The mixing lobes 26, 28 of the turbine shroud 20 in combination with ejector shroud 40 promote turbulent mixing of the lower velocity primary fluid stream 2 from the ejector shroud and the higher velocity secondary fluid stream 4. This turbulent mixing increases the overall velocity of the combined fluid stream 6 output from the ejector shroud 40. This turbulent mixing enhances the power output of the system by increasing the amount of fluid flow through the system, by increasing the velocity of the primary fluid stream at a plane of the rotor for more power availability, and by reducing the pressure on a down-wind side of the rotor plane.

FIG. 3 is a detail of the cross-section of a shrouded fluid turbine illustrating a shroud-tip gap. Each blade 70 includes a proximal portion 72 coupled to the central hub 62 at the blade root 73, a mid portion 74, and a distal portion 76 with a blade tip 77. As illustrated by FIG. 3, an inner surface 25 of the turbine shroud is separated from the blade tip 77 by a shroud-tip distance D_(G), which is the shroud-tip gap. Throughout the figures, the shroud-tip gap is exaggerated for illustrative purposes. FIGS. 27 and 28 are included to assist one skilled in the art to visualize and depict a shrouded turbine with a single shroud. As described above, all the blade tip-shroud clearance features taught herein are equally applicable to shrouded turbines having a single shroud, and shrouded turbines having more than one shroud.

As noted above, the shrouded fluid turbines of the present disclosure incorporate features for controlling, setting or adjusting the shroud-tip gap D_(G). The shroud-tip gap D_(G) may be changed by changing a distance between a blade tip and the central hub (e.g., D_(TH) depicted in FIG. 3), by changing a distance between the blade tip and the central axis (e.g., D_(TA) depicted in FIG. 3), by changing a distance between a portion of the shroud inner surface proximal to the blade tip and the central axis, (e.g., D_(SA) depicted in FIG. 3) or through any combination of the aforementioned. Accordingly, an adjustment mechanism of a shrouded fluid turbine may adjust the shroud-tip gap D_(G) by changing the blade tip-central hub distance D_(TH) or the blade tip-central axis distance D_(TA), by changing the shroud inner surface-central axis distance D_(SA), or through any combination of the aforementioned.

As explained above, adjustment mechanisms and shroud-tip clearance features described and depicted herein may be incorporated into shrouded fluid turbines having a single shroud and shrouded fluid turbines having more than one shroud (e.g., mixer-ejector shrouded fluid turbines). FIGS. 4 to 11 depict example shrouded fluid turbines having features for controlling, setting or adjusting the shroud-tip distance D_(G) by controlling, setting or adjusting the blade tip-central hub distance (e.g., D_(TH) depicted in FIG. 3). FIGS. 12 to 17 depict example shrouded fluid turbines having shroud-tip clearance features for controlling, setting or adjusting the shroud-tip distance D_(G) by controlling, setting or adjusting the shroud inner surface-central axis distance (e.g., D_(SA) depicted in FIG. 3). Some example embodiments include structures that may reduce the potential for destructive shroud-tip contact and/or that may reduce an effect of the shroud-tip gap on efficiency of the shrouded wind turbine (e.g., shrouded fluid turbine 810 of FIGS. 18 and 19, and shrouded fluid turbine 910 of FIG. 20). Some example embodiments control shroud-tip clearance D_(G) by repelling the blade tips from proximal shroud portions and vice versa (e.g., shrouded fluid turbine 1010 of FIGS. 21 and 22 and shrouded fluid turbine 1110 of FIGS. 23 and 24). Some example embodiments include additional features to set a shroud-tip clearance D_(G) through control of dimensions of a shroud inner surface (e.g., shrouded fluid turbine 1210 of FIGS. 25 and 26). Some example embodiments incorporate methods for setting, controlling or adjusting a shroud-tip gap D_(G) (e.g., method 2000 of FIG. 29, method 2010 of FIG. 30, method 2020 of FIG. 31, method 2030 of FIG. 32, method 2040 of FIG. 33 and method 2050 of FIG. 34).

FIGS. 4 and 5 depict an example shrouded fluid turbine 110 having an adjustment mechanism configured to adjust, set or control a separation between a blade tip and a shroud inner surface by lengthening or shortening a distance between the blade tip and a central hub. The shrouded fluid turbine 110 includes a turbine shroud 120 and a rotor 160 with blades 170, where each blade 170 has a retractable and extendable distal portion 176. As illustrated by detail view 101 of FIG. 4 and detail view 102 of FIG. 5, with the distal portion 176 in a retracted position, a distance D_(TH0) between a blade tip 177 and a central hub 162 of the rotor is relatively small, resulting in relatively large gap or clearance distance D_(GO) between the blade tip 177 and an inner surface 125 of the turbine shroud 120. For an example shrouded fluid turbine, a relatively large gap may be greater than or equal to 2% of the inner radius of the shroud, and a relatively small gap may be less than or equal to 0.5% of the inner radius of the shroud. With the distal portion 176 of the blade adjusted to an extended position, as indicated by dotted line 178, the blade tip-central hub distance is increased by an amount Δ_(TH1), which reduces the shroud-tip gap distance by a corresponding amount resulting in shroud-tip gap distance D_(G1). Thus, by extending and retracting the blade's distal portion 176, the shroud-tip gap D_(G) is adjusted. In some embodiments, the shrouded fluid turbine 110 may also include a second shroud, which may be referred to as an ejector shroud 140.

In some embodiments the blade's distal portion, the blade's mid-portion and/or the blade's proximal portion may be continuously adjustable to obtain any position between a fully extended position and a fully retracted position. In other embodiments, the blade's distal portion, the blade's mid-portion and/or the blade's proximal portion may be adjusted to one or more fixed positions between a fully extended position and a fully retracted position. Although in shrouded fluid turbine 110, the distal portion 176 of each blade is extendable and retractable, in some embodiments a distal portion, a mid portion and/or a proximal portion of a blade may be extendable and retractable.

FIGS. 6 and 7 illustrate another example shrouded fluid turbine 210 including an adjustment mechanism configured to adjust, set or change a separation between a blade tip and a shroud inner surface by lengthening or shortening a distance between the blade tip and a central hub. Shrouded fluid turbine 210 includes an adjustment mechanism in the form of a telescopically extendable and retractable blade 270 in which at least a distal portion 276 and a mid-portion 274 of the blade may be extended and retracted in a radial direction with respect to the central hub. Shrouded fluid turbine 210 includes a turbine shroud 220 and a rotor 260. As shown in detail view 201 of FIG. 6 and detail view 202 of FIG. 7, each blade 270 of rotor 260 telescopically extends and retracts along a radial direction with respect to the central axis of the shrouded fluid turbine, which may correspond to extension and retraction along a longitudinal axis of the blade. In some embodiments, the shrouded fluid turbine 210 may also include a second shroud, which may be referred to as an ejector shroud 240.

As illustrated by the side cross-sectional view of FIG. 7, when the blade 270 is in a retracted position, a distance D_(TH2) between the blade tip 277 and the central hub 262 is relatively small and the shroud-tip gap D_(G2) is relatively large. When the blade 270 is adjusted to a relatively extended position, indicated by dotted line 278 in detail 202 of FIG. 7, the tip-hub distance increases by an amount A_(TH3) and the shroud-tip gap D_(G3) is decreased by a corresponding amount. By telescopically extending and retracting the blade 270, the shroud-tip gap D_(G) is adjusted.

FIG. 8 illustrates another example shrouded fluid turbine 310 including an adjustment mechanism configured to adjust, set or change a separation between a blade tip and a shroud inner surface by lengthening or shortening a distance between the blade tip and a central hub. Shrouded fluid turbine 310 includes blades 370 that can be displaced along a radial axis with respect to a central hub 362 to change a distance D_(TH4) between a blade tip 377 and the central hub 362. As illustrated by detail view 301 of FIG. 8, a root 373 of the blade is configured to be displaced linearly with respect to a central hub 362 as indicated by arrow 380. Displacing the blade root 373 also displaces the blade tip 377, changing both the tip-hub distance D_(TH4) and a distance D_(G4) between a shroud inner surface 325 and the blade tip 377. In some embodiments, the shrouded fluid turbine 320 includes a single shroud, and in some embodiments the shrouded fluid turbine includes more than one shroud, for example a mixer-ejector combination.

One of skill in the art would recognize that extending or retracting a proximal portion of a blade (e.g., proximal portion 176 in FIGS. 4 and 5), telescopically extending or retracting a blade (e.g., blade 270 in FIGS. 6 and 7), or linearly displacing a blade root along a radial axis relative to a central hub (e.g., blade root 373 in FIG. 8), may be accomplished with many different types of passive and/or active actuators, including, but not limited to: mechanical actuators, hydraulic actuators, pneumatic actuators, electrical actuators, piezoelectric actuators, magnetic actuators and any combination of the aforementioned. Further, an actuation structure may extend and retract at least a portion of a blade, or linearly displace a blade root, while the blade root is rotationally engaged with a central hub (e.g., for control of blade pitch).

FIGS. 9 through 11 illustrate yet another example shrouded fluid turbine 410 that includes an adjustment mechanism configured to adjust, set or control a separation between a blade tip and a shroud inner surface by lengthening or shortening a distance between the blade tip and a central hub. Shrouded fluid turbine 410 includes a rotor 460 with blades 470 and a turbine shroud 420. In some embodiments, the shrouded fluid turbine 210 includes more than one shroud, for example, the turbine shroud 420 and an ejector shroud ejector shroud 240. Each blade 470 of the rotor includes a coupling (e.g., hinge 479) between a proximal portion 472 and a distal portion 476 of the blade that permits at least the distal portion 476 of the blade to be angularly displaced (e.g., rotated) about a non-radial axis 482 with respect to the proximal portion 472.

By varying an angular displacement of the distal portion 476 of the blade with respect to the proximal portion 472, a distance between a blade tip 477 and a central hub 462 can be set, adjusted or controlled. As shown in the side cross-section view of FIG. 9 and detail view 401 of FIG. 9, with the distal portion 476 of the blade in a straight position aligned with a mid-portion 274 and the proximal portion 474 (e.g., aligned with axis 480), a distance D_(TH6) between the blade tip 477 and the central hub 462 is relatively large, corresponding to a relatively small distance D_(G6) between a shroud inner surface 425 and a blade tip 477. As shown in detail view 402 of FIG. 10, with the distal portion 476 of the blade angularly displaced at about a 45 degree angle with respect to the axis 480 about the non-radial axis 482, the shroud-tip distance D_(G7) is relatively larger. As shown in detail view 403 of FIG. 11, with the distal portion 476 of the blade angularly displaced at about a 90 degree angle with respect to the axis 480 about the non-radial axis 482, the shroud-tip distance D_(G8) is even larger.

As used herein, the term “blade tip” refers to the portion of the blade that is closest to the shroud inner surface, which may depend on the current configuration of the blade. For example, with the distal portion of the blade aligned with axis 480, the “blade tip” refers to the terminal end portion of the blade. If the distal portion 276 of the blade were angularly displaced by more than 90 degrees with respect to axis 480, the “blade tip” would refer to the hinge 479, which would then be closest to shroud inner surface 425. Similarly, if the distal portion 476 were angularly displaced by more than 90 degrees, the shroud-tip gap or clearance distance would refer to the distance between the hinge 479 and the portion of the inner surface 425 proximal to the hinge.

One of ordinary skill in the art, in view of the described example embodiments, would recognize that many different configurations and structures could be employed to permit a distal portion of a blade to rotate about a non-radial axis with respect to a proximal portion of the blade. Although FIGS. 9 through 11 depict the coupling as a hinge, other couplings that permit a distal portion of the blade to be angularly displaced with respect to a proximal portion of the blade about a non-radial axis may be employed. For example, the coupling may be a castable elastomer engaged with both the distal and proximal portions of the blade.

Although FIGS. 9 through 11 depict the coupling between the proximal portion of the blade and the distal portion of the blade as located near the distal portion of the blade, the coupling may be located in the mid-portion of the blade or near the proximal portion of the blade, which would permit the distal portion and at least some of the mid-portion of the blade to rotate with respect to the proximal portion of the blade. Although FIGS. 9 through 11 depict the coupling as permitting rotation of the proximal portion of the blade about the axis 482, the coupling may permit angular displacement of at least the proximal portion of the blade about any non-radial axis.

FIGS. 12 to 17 depict example shrouded fluid turbines in which an adjustment mechanism is configured to adjust, set or control a distance between a blade tip and an inner surface of the shroud by controlling, setting or changing a distance between at least a portion of the inner surface and a central axis of the shrouded fluid turbine.

FIG. 12 illustrates a shrouded fluid turbine 510 that employs an inflatable bladder to control, set or change a shroud-tip clearance or gap. Shrouded fluid turbine 510 includes a central hub 562 rotatable about a central axis 518 of the shrouded fluid turbine, and blades 570 with each blade having a proximal portion 576 including a blade tip 577. Shrouded fluid turbine 510 also includes a turbine shroud 520 having an inner surface 525 in proximity to the blade tips 577. In some embodiments, the shrouded fluid turbine 510 may include an ejector shroud 540. The turbine shroud 520 may include the inflatable bladder 580. As depicted, the turbine shroud 520 includes a non-inflatable portion 529 on which the inflatable bladder 580 is disposed. The inflatable bladder 580 may be affixed to the non-inflatable portion 529, removably attached to the non-inflatable portion 529, integral with the non-inflatable portion 529 or coupled to the non-inflatable portion 529 in any other suitable manner. A surface 582 of the inflatable bladder 580 may form a portion of the inner surface 525 of the turbine shroud proximal to the blade tips 577. The side cross-sectional view of FIG. 12 illustrates a distance D_(SA9) between a portion of the shroud inner surface 525, which is the inflatable bladder surface 582, and the center axis 518. Detail view 501 of FIG. 12 illustrates a corresponding a shroud-tip distance D_(G9) between the shroud inner surface 525, which is the inflatable bladder surface 582, and the blade tip 577. Increased inflation of the inflatable bladder 580 moves the inflatable bladder surface 582 toward the central axis 518, as shown by broken line 584 reducing the shroud-axis distance by an amount A_(SA10) and reducing the shroud-tip gap to D_(G10). Thus, the shroud-axis distance D_(SA) and the shroud-tip spacing D_(G) can be changed through inflation or deflation of at least a portion of the inflatable bladder 580.

FIGS. 13 and 14 illustrate an example embodiment of a shrouded fluid turbine 610 that employs an inflatable bladder in a cavity of a turbine shroud to control, set or change a shroud-tip clearance or gap. Shrouded fluid turbine 610 includes a central hub 662 rotatable about a central axis 618 of the shrouded fluid turbine, and blades 670 with each blade 670 having a distal portion 676 including a blade tip 677. Shrouded fluid turbine 610 includes a turbine shroud 620 with an inflatable bladder 680 disposed in a cavity 690 of a non-inflatable portion 629 of the turbine shroud. In some embodiments, the shrouded fluid turbine 610 includes more than one shroud, for example, an ejector shroud downstream of the turbine shroud 620. As shown in detail 601 of FIG. 13, an inner surface 625 of the turbine shroud may include a layer 692 covering cavity 690 and inflatable bladder 680. FIG. 13 shows the inflatable bladder 680 in a less inflated state with a shroud-axis distance D_(SA11) and a corresponding distance D_(G11) between the shroud inner surface 625 and the blade tips 677. As illustrated in detail 602 of FIG. 14, with increased inflation, inflatable bladder 680 deflects outer layer 692, which forms a portion of shroud inner surface 625, toward the central axis 618, reducing the shroud-axis distance by an amount Δ_(SA12) and reducing the shroud-tip gap to D_(G12).

An inflatable bladder, (e.g., inflatable bladder 580 or FIG. 12, or inflatable bladder 680 of FIGS. 13 and 14) may include one inflatable chamber or a plurality of inflatable chambers. The plurality of inflatable chambers may be independently inflatable and/or the plurality of inflatable chambers may be in fluid communication with each other. For example, in FIG. 12, a first inflatable portion 585 in detail 501 is in a relatively less inflated state at the same time that a second inflatable portion 586 shown in detail 502 is in a fully inflated state.

An inflatable bladder may be coupleable to, affixed to or integral with a non-inflatable portion of the turbine shroud. The inflatable bladder may be removable or replaceable.

FIGS. 15 to 17 depict an example shrouded fluid turbine 710 that incorporates a hinged pitch mechanism configured to lengthen or shorten a distance between at least some inner surface portions of a turbine shroud and a central axis. Shrouded fluid turbine 710 includes a central hub 762 rotatable about a central axis 718 of the shrouded fluid turbine, and blades 770. Each blade 770 has a proximal portion 776 including a blade tip 777. The shrouded fluid turbine 710 includes a turbine shroud 720. In some embodiments, the shrouded fluid turbine 710 also includes an ejector shroud 740. The turbine shroud 720 includes hinged shroud portions extending downstream and inward toward the central axis (inwardly extending hinged shroud portions) 782 and hinged shroud portions extending downstream and outward away from the central axis (outwardly extending hinged shroud portions) 784. The inwardly extending hinged shroud portions 782 and the outwardly extending hinged shroud portions 784 (collectively “hinged shroud portions”) tilt to change the pitch of parts of the turbine shroud. FIG. 16 shows the shrouded fluid turbine 710 with the hinged shroud portions 782, 784 in a relatively low pitch configuration in which a distance between a portion of an inner surface 725 of the turbine shroud proximal to the blade tips 777 and the central axis 718 is D_(SA13) and a shroud-tip gap D_(G14) is relatively small. FIG. 17 shows the shrouded fluid turbine 710 with the hinged portions 782, 784 in a relatively high pitch configuration with a larger shroud-axis distance D_(SA13), and a larger shroud-tip gap D_(G14).

The shrouded fluid turbine 710 may include a control mechanism to control the positions of at least some of the inner surface portions relative to the central axis 718. For example, one or more levers 786 may be used to control the tilt of the hinged portions 784, as shown. In some example embodiments the control mechanism may individually and independently control the position of each hinged inner surface portion for a plurality of the inner surface portions. In some example embodiments the control mechanism may control the positions of the hinged inner surface portions as a group.

The shrouded fluid turbine 710 may include one or more sensors 792 for sensing or detecting a spacing between the shroud inner surface 725 and the blade tip 777 or between the shroud inner surface 725 and the central axis 718. The sensors may be optical, electrical, electro-magnetic, mechanical or may employ any other suitable sensing mode.

One of ordinary skill in the art would recognize that other control mechanisms could be employed to adjust a pitch of turbine shroud segments, including, but not limited to rotational actuator motors, torsion bars, linear motorized actuators, pneumatic or hydraulic pistons and the like.

As noted above, some example embodiments of shrouded fluid turbines include structures that may reduce the potential for destructive shroud-tip contact and/or that may reduce an effect of the shroud-tip gap on efficiency of the shrouded wind turbine. FIGS. 18 and 19 depict an example shrouded fluid turbine 810 having a rotor that includes a blade ring and a turbine shroud that has a radial recess into which the blade ring extends. Shrouded fluid turbine 810 includes a rotor 860 that has a central hub 862 rotatable about a central axis 818 of the fluid turbine, a blade ring 864, and one or more blades 870. Each blade 870 has a proximal portion 872 including a blade root 873 coupled to the central hub 862, a distal portion 876 including a blade tip 877 and a mid-portion 874 disposed between the proximal portion 872 and the distal portion 876. The blade ring 864 extends circumferentially about the central axis 818 and is coupled to the distal portion 876 of the blades. The shrouded fluid turbine 810 has an inner surface 825 in proximity to the blade tips 877 and may include mixing lobes 826, 828. The turbine shroud 820 has a body 880 that defines a radial recess 882 in the inner surface 825 of the turbine shroud. As illustrated, the blade ring 864 extends, at least partially, into the recess 882 of the turbine shroud. In some embodiments, the shrouded fluid turbine may also include an ejector shroud 840 downstream of the turbine shroud 820 and an outlet of the turbine shroud may extend into an inlet of the ejector shroud.

A shroud-tip clearance or gap is defined between an outer surface of the blade ring 864 and inner surface 825 of the turbine shroud at the recess 882. A size of the shroud-tip gap may have a reduced effect on efficiency of the shrouded fluid turbine 810 because fluid flowing through the gap cannot flow along a straight path, but instead must flow into the recess 882, around the blade ring 864 and out of the recess 882.

The blade ring 864 provides some mechanical support to the blade tips 877 and may reduce the amount that the blades 870 elastically or plastically deform, which may reduce the chance of incidental contact with the inner surface 825 of the turbine shroud 820. Further, the potential for destructive contact between the rotor 860 and the turbine shroud 820 may be reduced because incidental contact between the rotor 860 and the turbine shroud 820 occurs at the blade ring 864 instead of at tips of individual unsupported blades.

Some example embodiments may incorporate a blade ring that fully extends into a radial recess of a turbine shroud, or a blade ring that only partially extends into a radial recess of a turbine shroud. Some example embodiments may incorporate a blade ring, but not a radial recess in the turbine shroud. Some example embodiments may incorporate a radial recess in the turbine shroud without a blade ring.

FIG. 20 depicts an example energy extraction shrouded fluid turbine 910 including a turbine shroud with an inner surface including an abradable material. Shrouded fluid turbine 910 includes a rotor 960 with a central hub 962 rotatable about a central axis 918 of the shrouded fluid turbine and a blade 970. The blade 970 has a proximal portion 972 including a blade root 973 coupled to the central hub 962, a distal portion 976 including a blade tip 977 and a mid-portion 974 disposed between the proximal portion 972 and the distal portion 976. Shrouded fluid turbine 910 further includes a turbine shroud 920 with an inner surface 925 in proximity to the blade tips 977 and mixing lobes 926. In some embodiments, the shrouded fluid turbine 910 also includes an ejector shroud 940 located downstream of the turbine shroud 920. At least a portion the inner surface 925 of the turbine shroud includes an abradable material 980 having a hardness less than a hardness of the blade tip 977. The blade tips 977 may include a material 978 having a hardness less than that of a blade tip 977. The blade 970 may have a proximal portion 976 including a high hardness or abrasive material 978 at the blade tips 977. The blade tip 977 may occasionally or continuously contact the inner surface 925 during rotation of the rotor 960. Incidental contact between the high hardness blade tips 977 and the abradable material 980 of the shroud inner surface 925 during rotation of the rotor 960 may form a groove or recess 986 in the shroud inner surface 925.

In other embodiments, an inner shroud surface may comprise a high hardness material or an abrasive high hardness material and a blade tip may comprise an abradable material. In these embodiments, during use, intermittent or continuous contact between the blade tip and the inner shroud surface would abrade the blade tip.

The abradable shroud inner surface or the abradable blade tip may comprise a foam, a foam with a thin skin of fiber reinforced polymer (FRP), or another suitable material. A hard abrasive blade tip or a hard abrasive shroud inner surface may comprise a structural FRP additionally impregnated with a granular substance, such as sand or metal filings, that would make a rough surface to wear away the abradable material.

Some shrouded fluid turbines may include a clearance control mechanism that repels a blade tip from at least some of the shroud inner surface portions or that repels at least some of the shroud inner surface portions from the blade tip. For example, FIGS. 21 and 22 depict a shrouded fluid turbine 1010 including a clearance control mechanism in which blade tips are magnetically repelled from at least some shroud inner surface portions. Shrouded fluid turbine 1010 includes a central hub 1062 and blades 1070 that rotate about a central axis 1018 of the shrouded fluid turbine. Each blade 1070 includes a proximal portion 1072 with a blade root 1073 coupled to the central hub 1062 a distal portion 1076 including a blade tip 1077 and a mid-portion 1074 disposed between the proximal portion 1072 and the distal portion 1074. Shrouded fluid turbine 1010 includes a turbine shroud 1020 and may include an ejector shroud 1040. As illustrated by detail 1001 of FIG. 21 and detail 1002 of FIG. 22, turbine shroud 1020 includes a body 1080 and a ring of magnets 1082. A distal portion 1076 of each blade includes a material that is repelled by the magnetic field produced by the ring of magnets 1082 in the turbine shroud 1020. For example, a distal portion 1076 may include a permanent magnetic material (e.g., a ferromagnetic material) arranged such that the poles of the permanent magnetic material in the blades oppose the poles of the magnets 1082 in the turbine shroud 1020. As another example, the proximal portion 1076 of the each blade may include a strongly diamagnetic material. Blade tips 1077 are magnetically repelled by at least portions of the turbine shroud 1020 thereby controlling the shroud-tip clearance distance D_(G15). In some embodiments, portions of the turbine shroud 1020 may be repelled by the blade tips 1077. In some embodiments, the clearance control mechanism includes one or more electromagnets.

FIGS. 23 and 24 depict an example shrouded fluid turbine 1110 incorporating a clearance control mechanism that repels a blade tip from at least some of the shroud inner surface portions, a rotor that incorporates a blade ring, and a turbine shroud having a radial recess into which the blade ring extends. Shrouded fluid turbine 1110 includes a rotor 1160 having a blade ring 1164 coupled to distal portions 1176 of blades 1170. Shrouded fluid turbine 1110 also includes a turbine shroud 1120 with a body 1180 defining a recess or groove 1184 into which the blade ring 1164 at least partially extends. Turbine shroud 1120 further includes magnets 1182 disposed proximal to the recess or groove 1184. Blade ring 1164 also includes a magnetic material arranged so that the polarity of the blade ring 1164 opposes the polarity of the turbine shroud magnets 1182, resulting in the blade ring 1164 being repelled by the shroud inner surface 1125 and/or the shroud inner surface 1125 being repelled by the blade ring 1164. In some embodiments, shrouded fluid turbine 1110 further includes an ejector shroud 1140.

FIGS. 25 and 26 depict a shrouded fluid turbine with precise control of dimensions of a shroud inner surface. Shrouded fluid turbine 1210 includes a rotor 1260 and a turbine shroud 1220 having a front end portion 1222 and a rear end portion 1224. As shown in FIG. 26, the front end portion 1222 has an inner surface 1223 that forms the inner surface 1225 of the turbine shroud that is proximal to tips 1277 of blades 1270. The rear end portion 1224 of the turbine shroud includes low energy mixing lobes 1226 and high energy mixing lobes 1228. The front end portion 1222 of the turbine shroud may be formed, cast, machined or otherwise made with relatively high precision control of a radius R_(s) of the inner surface 1223. For example, the radius R_(s) of the inner surface of the font end portion 1222 of the shroud may have a precision of at least 50% of the tip gap. For some embodiments the tip gap is between 0.5% and 2% of the inner radius of the shroud, resulting in a precision of at least between 0.25% and 1%. Further, the front end portion 1222 may have a structure that is resistant to deformation (e.g., rigid carbon fiber, steel or aluminum spars and struts with a rigid outer surface; or an inner foam structure with a FRP skin) and/or may comprise a material that is particularly resistant to deformation (e.g., carbon fiber, steel, aluminum or the like for the inner structure combined with a lightweight skin such as aluminum or FRP; or a light weight foam core with an integral skin) to maintain the precise inner surface radius during use. The front end portion 1222 may include multiple segments coupled together or may be one unitary piece. The front end portion 1222 may be cast, molded, formed, machined or manufactured using any combination of techniques that produce a high precision inner surface radius. The rear end portion 1224, which includes the low energy mixing lobes 1126 and the high energy mixing lobes 1128, may be manufactured with a method suitable for producing the mixing lobe structures, which may be different method or combination of techniques than that used to produce front end portion. The front end portion 1222 is coupled with, or affixed to, the rear end portion 1224. The front end portion 1222 may be detachable or replaceable. In some embodiments, the shrouded fluid turbine 1210 further includes a mixer shroud downstream of the turbine shroud.

FIGS. 27 and 28 depict an example shrouded fluid turbine 1310 in which features for controlling, setting or adjusting a gap spacing between a blade tip and shroud inner surface may be incorporated. The shrouded fluid turbine 1310 includes a turbine shroud 1320, a nacelle body 1350, and a rotor 1340 that encircles the nacelle body. As illustrated by FIG. 28, the rotor 1340 and turbine shroud 1320 may be coaxial with each other, (i.e., all share the common central axis 1318). The turbine shroud 1320 includes a front end 1312, also known as an inlet end or a leading edge, and a rear end 1315, also known as an exhaust end or trailing edge. As illustrated by FIGS. 27 and 28, the rotor 1340 includes one or more blades 1370 connected to a central hub 1341. As used herein, any description of, or reference, to “a blade” or “the blade” refers to some or all blades of a rotor. Although the rotor 1340 in FIGS. 27 and 28 is depicted with three blades in other embodiments, the rotor may include two blades, three blades, four blades or more blades.

Although turbine shroud 1320 in FIGS. 27 and 28 is shown encircling the rotor 1340, in some example embodiments the turbine shroud 1320 may only partially encircle the rotor (e.g., the turbine shroud may have gaps, or the rotor may extend beyond the leading edge or trailing edge of the turbine shroud). In some embodiments, the turbine shroud may not encircle the rotor (e.g., the rotor may be positioned in front of the leading edge or past the trailing edge of the turbine shroud).

As illustrated by FIG. 28, the turbine shroud 1320 may have the cross-sectional shape of an airfoil 1380 with the suction side (i.e., low pressure side) on the interior of the shroud. Referring again to FIGS. 27 and 28, the rear end 1315 of the turbine shroud 1320 may include mixing lobes 1316 that may extend downstream beyond the rotor blades 1370. As shown, the mixing lobes 1316 may include low energy mixing lobes that extend inward toward the central axis 1318 and high energy mixing lobes that extend outward away from the central axis 1318. In other words, the rear end 1315 of the turbine shroud is shaped to form two different sets of mixing lobes. The turbine shroud 1320 may define an opening 1317 or channel located between a low energy mixing lobe and a high energy mixing lobe that increases mixing between high and low energy streams. This turbulent mixing may enhance the power output of the system by increasing the amount of fluid flow through the system, by increasing the velocity of the primary fluid stream at a plane of the rotor for more power availability, and by reducing the pressure on a down-wind side of the rotor plane.

FIG. 28 includes a detailed depiction of a cross-section 1302 of fluid turbine 1310 illustrating a shroud-tip gap. Each blade 1370 includes a proximal portion 1372 coupled to the central hub 1341 at the blade root 1373, a mid-portion 1374, and a distal portion 1376 with a blade tip 1377. As illustrated by FIG. 28, an inner surface of the turbine shroud 1320 is separated from the blade tip 77 by a shroud-tip distance D_(G16), which is the shroud-tip gap. In FIG. 28, a size of the shroud-tip gap is exaggerated for illustrative purposes.

Some example embodiments are directed to methods that employ shrouded fluid turbines. FIG. 29 schematically illustrates a method 2000 of adjusting a blade tip-shroud gap spacing in an energy extraction shrouded fluid turbine that includes a central hub rotatable about a central axis of the shrouded fluid turbine, a blade having a blade tip and a turbine shroud having an inner surface in proximity to the blade tip. In some embodiments, the energy extraction shrouded fluid turbine may further include an ejector shroud and the turbine shroud may include mixing lobes.

For illustrative purposes, method 2000 is described with respect to the shrouded fluid turbine 110 depicted in FIGS. 4 and 5; however, one of skill in the art will recognize that method 2000 may be implemented using other configurations of shrouded fluid turbines that have features for adjusting a spacing between a blade tip and the central hub of the shrouded fluid turbine. For example, method 2000 may be implemented using shrouded fluid turbine 210 of FIGS. 6 and 7, using shrouded fluid turbine 310 of FIG. 8, or using shrouded fluid turbine 410 of FIG. 9. As another example, method 2000 may be implemented using a single shroud version of any of the shrouded turbines depicted in FIGS. 4 through 9.

Method 2000 includes sensing a spacing between the blade tip 177 and at least a portion of the inner surface 125 of the turbine shroud during rotation of the blade about the central axis (method portion 2002). Sensing the spacing between the blade tip 177 and at least a portion of the inner surface 125 of the turbine shroud 120 may include detecting a radial position of the blade tip 177 relative to the central axis 118, relative to the central hub 162, or relative to the shroud inner surface 125. The spacing between the blade tip 177 and at least a portion of the shroud inner surface 125 may be sensed optically, electrically, electromagnetically, mechanically or using any other suitable sensing mode.

Method 2000 also includes changing a distance D_(TH) between the blade tip 177 and the central hub 162 in response to the sensed spacing (method portion 2004). Changing a distance between the blade tip and the central hub may include extending or retracting at least a portion of the blade with respect to the central hub (see e.g., detail 101 of FIG. 4, detail 102 of FIG. 5, detail 201 of FIG. 6 and detail 202 of FIG. 7). At least a portion of the blade may be extended or retracted telescopically (see e.g., detail 101 of FIG. 4, detail 102 of FIG. 5, detail 201 of FIG. 6 and detail 202 of FIG. 7). Changing a distance between the blade tip and the central hub may include displacing at least the blade tip and the blade mid-portion in a radial direction with respect to the central hub (see, e.g., detail 301 of FIG. 8). Displacing at least a portion of the blade in a radial direction with respect to the central hub may be displacing at least a portion of the blade along a longitudinal axis of the blade.

Changing a distance between the blade tip and the central hub may include rotating at least the distal portion of the blade relative to the proximal portion of the blade, or relative to the central hub, about a non-radial axis (see, e.g., FIGS. 9 to 11). The distance between the blade tip and the central hub may be changed in real time during operation of the shrouded fluid turbine.

FIG. 30 schematically illustrates a method 2010 of adjusting a blade tip-shroud gap spacing in an energy extraction shrouded fluid turbine including a central hub rotatable about a central axis of the energy extraction shrouded fluid turbine, a blade having a blade tip, and a turbine shroud having an inner surface in proximity to the blade tip. The turbine shroud of the energy extraction shrouded fluid turbine may include mixing lobes. The energy extraction shrouded fluid turbine may further include an ejector shroud. For illustrative purposes, method 2010 will be described with respect to shrouded fluid turbine 510 of FIG. 12; however, one of skill in the art will recognize that method 2010 may be implemented using other configurations of shrouded fluid turbines that have features for adjusting a spacing between a blade tip and at least a portion of a shroud inner surface. For example, method 2010 may be implemented using shrouded turbine 610 of FIGS. 13 and 14, or using shrouded turbine 710 of FIGS. 15 through 17. As another example, method 2010 may be implemented using a single shroud version of any of the shrouded fluid turbines depicted in FIGS. 12 through 17.

Method 2010 includes sensing a spacing between the blade tip 577 and at least a portion of the inner surface 525 of the turbine shroud 520 during rotation of the blade 570 about the central axis 518 (method portion 2012). Sensing the spacing between the blade tip 577 and at least a portion of the inner surface 525 of the turbine shroud 520 may include detecting a radial position of the blade tip 577 relative to the central axis 518 or relative to the shroud inner surface 525, or detecting a radial position of at least a portion of the shroud inner surface 525 relative to the central axis 518. The spacing between the blade tip 577 and at least a portion of the shroud inner surface 525 may be sensed optically, electrically, electromagnetically, mechanically or using any other suitable sensing mode.

Method 2010 also includes changing a distance between at least a portion of the shroud inner surface 525 and the central axis 518 based on the sensed spacing (method portion 2014). Changing a distance between at least a portion of the shroud inner surface 525 and the central axis 518 may occur during operation of the energy extraction turbine and during rotation of the blade 570.

The energy extraction shrouded fluid turbine may further include an inflatable bladder associated with the shroud inner surface (see e.g., inflatable bladder 580 of FIG. 12, inflatable bladder 680 of FIG. 13). Changing a distance between at least a portion of the shroud inner surface and the central axis may comprise inflating or deflating at least a portion of the inflatable bladder (see e.g., detail 501 of FIG. 12 and details 601 and 602 of FIG. 13).

The energy extraction shrouded fluid turbine may further include a hinged pitch mechanism (see e.g., FIGS. 15 to 17). The distance between at least a portion of the shroud inner surface and the central axis may be changed using the hinged pitch mechanism (see e.g., FIGS. 16 to 17).

FIG. 31 schematically illustrates a method 2020 of controlling a blade tip-shroud gap spacing in an energy extraction shrouded fluid turbine including a central hub rotatable about a central axis of the energy extraction shrouded fluid turbine, a blade having a blade tip and a first shroud having an inner surface in proximity to the blade tip. For illustrative purposes, method 2020 is described with respect to the shrouded fluid turbine 110 depicted in FIGS. 4 and 5; however, one of skill in the art will recognize that method 2020 may be implemented using other configurations of shrouded fluid turbines that have features for actively controlling a distance between a blade tip and a central hub based on a detected spacing. For example, method 2020 may be employed using any of the shrouded fluid turbines in FIGS. 4 through 11, or using a single shroud version of any of the shrouded fluid turbines in FIGS. 5 through 11.

Method 2020 includes detecting a spacing between the blade tip 177 and at least a portion of the shroud inner surface 125 during rotation of the blade 170 about the central axis 162 (method portion 2022). Method 2020 also includes actively controlling a distance between the blade tip 177 and the central hub 162 during rotation of the blade 170 based on the detected spacing (method portion 2024). Actively controlling a distance between the blade tip and the central hub during rotation of the blade may include changing the distance between the blade tip and the central hub in real-time during operation of the shrouded fluid turbine (see, e.g., FIGS. 4 to 11).

Actively controlling a property implies calculating, measuring, sensing or determining one or more parameters of a system and changing or maintaining a physical and/or electromagnetic property of the system in response to the one or more calculated, measured, sensed or determined parameters to obtain or maintain a desired value of the controlled property. Passively controlling a property implies that the system itself adjusts to maintain a desired property, but the adjustment is not in response to a calculated, measured, sensed or determined parameter.

FIG. 32 schematically illustrates a method 2030 of controlling a blade tip-shroud gap spacing in an energy extraction shrouded fluid turbine including a central hub rotatable about a central axis of the energy extraction shrouded fluid turbine, a blade having a blade tip and a first shroud having an inner surface in proximity to the blade tip. For illustrative purposes, method 2030 is described with respect to the shrouded fluid turbine 710 depicted in FIGS. 15 through 17.

Method 2030 includes detecting a spacing between the blade tip 777 and at least a portion of the shroud inner surface 725 during rotation of the blade 770 about the central axis 762 (method portion 2032). Method 2030 also includes actively controlling a distance between at least a portion of the shroud inner surface 725 and the central axis 762 during rotation of the blade 770 based on the detected spacing (method portion 2024); however, one of skill in the art will recognize that method 2030 may be implemented using other configurations of shrouded fluid turbines that have features for actively controlling a distance between a blade tip and at least a portion of a shroud inner surface based on a detected spacing. For example, method 2030 may be employed using any of the shrouded fluid turbines in FIGS. 12 through 17, or using a single shroud version of any of the shrouded fluid turbines in FIGS. 12 through 17.

The shrouded fluid turbine may include an inflatable bladder (see e.g., inflatable bladder 580 of FIG. 12, inflatable bladder 680 of FIG. 13). A distance between at least a portion of the shroud inner surface and the central axis may be changed during rotation of the blade about the central axis by inflating or deflating at least a portion of the inflatable bladder (see e.g., detail 501 of FIG. 12 and details 601 and 602 of FIG. 13). As illustrated by FIG. 12, different sections of an inflatable bladder may be in different states of inflation. The state of inflation of each inflatable bladder section may be independently controlled.

The energy extraction shrouded fluid turbine may further include a hinged pitch mechanism (see e.g., FIGS. 15 to 17). The hinged pitch mechanism may be used to change the distance between at least a portion of the shroud inner surface and the central axis (see e.g., FIGS. 16 and 17).

FIG. 33 schematically illustrates a method 2040 of controlling a blade tip-shroud gap spacing in an energy extraction shrouded fluid turbine including a central hub rotatable about a central axis of the energy extraction shrouded fluid turbine, a blade having a blade tip, a turbine shroud having inner surface portions in proximity to the blade tip and a clearance control mechanism. For illustrative purposes, method 2040 is explained with respect to shrouded fluid turbine 1010 of FIGS. 21 and 22; however, one of skill in the art will recognize that method 2040 may be implemented using other configurations of shrouded fluid turbines that can incorporate a clearance control mechanism. For example, method 2040 may be employed using any of the shrouded fluid turbines in FIGS. 21 through 24, or using a single shroud version of any of the shrouded fluid turbines in FIGS. 21 through 24.

Method 2040 includes repelling the blade tip 1077 from at least some of the shroud inner surface portions 1025 or repelling at least some of the shroud inner surface portions 1025 from the blade tip 1077 during rotation of the blade 1070 about the central axis 1018 using the clearance control mechanism (method portion 2042). The clearance control mechanism may include ferromagnetic material (e.g., magnets 1082) disposed in at least one of the blade tip 1077 and the turbine shroud 1020. The clearance control mechanism may include electromagnets. The blade tip 1077 may be repelled from at least some of the shroud inner surface portions 1025, or at least some of the inner surface portions 1025 may be magnetically repelled from the blade tip 1077.

FIG. 34 schematically illustrates a method 2050 of controlling a shroud-blade tip spacing. Solely for illustrative purposes, method 2050 is explained with reference to example shrouded fluid turbine 910 of FIG. 20; however, one of skill in the art will recognize that method 2050 may be implemented using other configurations of shrouded fluid turbines, such as a single shroud version of shrouded fluid turbine 910. Method 2050 includes providing an energy extraction shrouded fluid turbine 910 (method portion 2052). The energy extraction shrouded fluid turbine 910 includes a rotor 960 with a central hub rotatable about a central axis 918 of the energy extraction shrouded fluid turbine 910, a blade 970 and a turbine shroud 920. The blade 970 includes a proximal portion 972 with a blade root 973 coupled to the central hub 962, a distal portion 976 with a blade tip 977 and a mid-portion 974 disposed between the proximal portion 972 and the distal portion 976. The turbine shroud 920 includes an inner surface 925 in proximity to the blade tip 977. The inner surface 925 includes an abradable material 978 having a hardness less than a hardness of the blade tip 977.

Method 2050 also includes forming a radial groove or trough 986 in the inner surface 925 of the turbine shroud 920 by at least intermittent contact with the blade tip 977 upon rotation of the blade 977. The radial groove or trough 986 may be formed, at least in part, before installation of the shrouded fluid turbine, may be formed at least in part, during installation of the shrouded fluid turbine, and/or may be formed, at least in part, during use of the shrouded fluid turbine.

The example shrouded fluid turbines described herein may be incorporated into a shrouded fluid turbine system that includes controllers for controlling one or more fluid turbines. One or more shrouded fluid turbine systems may, in turn, form a portion of a larger shrouded fluid turbine array system for decentralized energy generation.

The example embodiments may be utilized in conjunction a variety of forms of decentralized energy resources. One skilled in the art will recognize that the fluid turbine arrangements may be utilized in the generation of power in conjunction with overall power production in large-scale power grids. To ensure stable and controllable power production the shrouded fluid turbines may be interfaced with the power grid in a variety of suitable ways. One suitable approach for controlling and monitoring the output of a shrouded fluid turbine array system is a Supervisory Control And Data Acquisition (SCADA) system. A SCADA system for use with a shrouded fluid turbine array typically includes input/output signal hardware and controllers at the various location(s) to be monitored and/or controlled, a SCADA hub for monitoring and controlling the location(s), a communication link(s) from the location(s) to the SCADA hub, and one or more supervisory stations at location(s) remote from the SCADA hub and in communication with the SCADA hub.

As schematically represented in FIG. 35, a shrouded fluid turbine array system 2090 may include an array of shrouded fluid turbines 2092, and a SCADA system 2094 that controls the array of shrouded fluid turbines and interfaces with a power grid 2096. The array of shrouded fluid turbines 2092 may include single shroud fluid turbines, shrouded fluid turbines each having more than one shroud, or both. A SCADA system for use with a shrouded fluid turbine array may be configured to collect a large amount of data from one or more shrouded fluid turbines to which it is connected. Additionally, the SCADA system may be configured to control one or more shrouded fluid turbines to which it is connected by means of control routines feeding control parameters and settings to a fluid turbine assembly, so that a stable and controlled power supply can be ensured. Ensuring a stable and controllable power generation from one or more fluid turbines may include the use of meteorological modeling to predict changes in power production from fluid turbine generators. In accordance with an example embodiment, a SCADA system may use data derived from monitoring the power output from the fluid turbine generators of a turbine farm and the power transmission line. In accordance with this embodiment, the power output may be predicted using system-modeling algorithms understood in the art, and the power generation is stabilized by storing or releasing generated power in unstable periods. Such system-modeling algorithms may be based on meteorological predictions as well as a variety of suitable alternative modeling and prediction data.

FIG. 36 illustrates an example computing environment that may form at least a portion of a shrouded turbine control system, or a SCADA system for a shrouded fluid turbine array. As noted above, the environment may include one or more turbine control devices 2100 coupled, wired, wirelessly or a hybrid of wired and wirelessly, to one or more shrouded fluid turbines. The turbine control device 2100 is programmable to implement executable turbine control code 2150 for operating a shrouded fluid turbine. The executable turbine control code 2150 may include code for setting, adjusting or controlling a tip-shroud gap in a shrouded fluid turbine. The executable turbine control code 2150 may include code for setting or adjusting a tip-shroud gap during an initial set-up or installation of the shrouded fluid turbine and/or may include code for setting adjusting or controlling a tip-shroud gap during operation of the shrouded fluid turbine while a blade is rotating.

Turbine control device 2100 includes one or more computer-readable media for storing one or more computer-executable instructions or software for implementing example embodiments. For example, a memory 2106 of the turbine control device 2100 may store computer-executable instructions or software, e.g., instructions for implementing and processing every module of the executable turbine control code 2150. The computer-readable media may include, but are not limited to, one or more types of hardware memory, non-transitory tangible media, etc. The memory 2106 may comprise a computer system memory or random access memory, such as DRAM, SRAM, EDO RAM, etc. The memory 2106 may comprise other types of memory as well, or combinations thereof. The turbine control device 2100 may also include, or be in communication with, computer readable storage 2116 (e.g., a hard-drive, CD-ROM, or other non-transitory computer readable media) which may store the turbine control code 2150 and an operating system 2118.

The turbine control device 2100 includes a processor 2102, and may include one or additional more processor(s) 2103, for executing software stored in the memory 2106 and other programs for controlling system hardware. The processor 2102 and additional processor(s) 2103 may each have one or more core processors 2104 and 2105.

Virtualization may be employed in turbine control device 2100 so that infrastructure and resources in the computing device can be shared dynamically. Virtualized processors may also be used with the executable turbine control code 2150 and other software in storage 2116. A virtual machine 2114 may be provided to handle a process running on multiple processors so that the process appears to be using only one computing resource rather than multiple. Multiple virtual machines can also be used with one processor.

A user or operator of the shrouded fluid turbine system, or shrouded fluid turbine array system, may interact with the turbine control device 2100 through a visual display device 2122, such as a computer monitor, which may display the user interface 2124 or any other interface. The visual display device 2122 may also display other aspects or elements of example embodiments, (e.g., control and performance information regarding individual shrouded fluid turbines, control and performance information regarding the array of shrouded fluid turbines, information regarding the interface with the power grid). The turbine control device 2100 may include other I/O devices such a keyboard or a multi-point touch interface 2108 (e.g., a touch screen or touchpad), and a pointing device 2110, (e.g., a mouse or optical trackball) for receiving input from a user. The keyboard 2108 and the pointing device 2110 may be connected to the visual display device 2122. The turbine control device 2100 may include other suitable conventional I/O peripherals.

Turbine control device 2100 may include a network interface 2112 to interface to a Local Area Network (LAN), Wide Area Network (WAN) or the Internet through a variety of connections including, but not limited to, standard telephone lines, LAN or WAN links (e.g., 802.11, T1, T3, 56kb, X.25), broadband connections (e.g., ISDN, Frame Relay, ATM), wireless connections, controller area network (CAN), or some combination of any or all of the above. The network interface 2112 may comprise a built-in network adapter, network interface card, PCMCIA network card, card bus network adapter, wireless network adapter, USB network adapter, modem or any other device suitable for interfacing turbine control device 2100 to any type of network capable of communication and performing the operations described herein. Moreover, control device 2100 may be any computer system such as a workstation, desktop computer, server, laptop, handheld computer or other form of computing or telecommunications device that is capable of communication and that has sufficient processor power and memory capacity to perform the operations described herein. In some embodiments, one or more remote servers(s) may perform at least some processing for a user or operator using a local device to communicate with the remote server(s).

Turbine control device 2100 can be running any operating system such as any of the versions of the Microsoft® Windows® operating system, the different releases of the Unix and Linux operating systems, any version of the MacOS® operating system, any embedded operating system, any real-time operating system, any open-source operating system, any proprietary operating system, any operating systems for mobile computing devices, any internet delivered or internet based operating systems, or any other operating system capable of running on a computing device and performing the operations described herein. The operating system may be running in native mode or emulated mode.

Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this disclosure. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.

The term “about” when used with a quantity includes the stated value and also has the meaning dictated by the context. For example, it includes at least the degree of error associated with the measurement of the particular quantity. When used in the context of a range, the term “about” should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the range “from about 2 to about 4” also discloses the range “from 2 to 4.”

In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. §112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function. 

1. A shrouded fluid turbine comprising: a central hub rotatable about a central axis of the shrouded fluid turbine; a blade comprising: a proximal portion including a blade root coupled to the central hub; a distal portion including a blade tip; and a mid-portion disposed between the proximal portion and the distal portion; a first shroud having an inner surface in proximity to the blade tip; and an adjustment mechanism configured to adjust a separation between the blade tip and the shroud inner surface by lengthening or shortening a distance between the blade tip and the central hub.
 2. The shrouded fluid turbine of claim 1, further comprising an ejector shroud located downstream from the first shroud; wherein the first shroud comprises mixing lobes.
 3. The shrouded fluid turbine of claim 1, wherein the adjustment mechanism radially retracts or extends at least a portion of the blade with respect to the central hub.
 4. The shrouded fluid turbine of claim 3, wherein the adjustment mechanism retracts or extends at least a portion of the blade telescopically.
 5. The shrouded fluid turbine of claim 1, wherein the adjustment mechanism displaces at least the distal portion and the mid-portion of the blade in a radial direction with respect to the central hub.
 6. The shrouded fluid turbine of claim 1, wherein the adjustment mechanism comprises a coupling between at least the distal portion of the blade and the proximal portion of the blade that permits at least the distal portion of the blade to be rotationally displaced about a non-radial axis relative to the proximal portion of the blade.
 7. The shrouded fluid turbine of claim 6, wherein the adjustment mechanism comprises a hinge coupling the distal portion of the blade and the proximal portion of the blade.
 8. The shrouded fluid turbine of claim 1, wherein the adjustment mechanism comprises a hinged coupling that permits at least the proximal portion of the blade to be angularly displaced about a non-radial axis relative to the central hub.
 9. A shrouded fluid turbine comprising: a central hub rotatable about a central axis of the shrouded fluid turbine; a blade comprising: a proximal portion including a blade root coupled to the central hub; a distal portion including a blade tip; and a mid-portion disposed between the proximal portion and the distal portion; a first shroud having an inner surface in proximity to the blade tip; and an inflatable bladder associated with the inner surface and configured to change a spacing between the blade tip and the inner surface by changing a distance between at least a portion of the inner surface and the central axis upon inflation or upon deflation of at least a portion of the inflatable bladder.
 10. The shrouded fluid turbine of claim 9, further comprising an ejector shroud located downstream from the first shroud; wherein the first shroud comprises mixing lobes.
 11. The shrouded fluid turbine of claim 9, wherein the inflatable bladder is coupleable to the first shroud.
 12. The shrouded fluid turbine of claim 9, wherein the inflatable bladder is integral to the first shroud.
 13. The shrouded fluid turbine of claim 9, wherein the inflatable bladder comprises a plurality of inflatable chambers.
 14. A shrouded fluid turbine comprising: a central hub rotatable about a central axis of the shrouded fluid turbine; a blade comprising: a proximal portion including a blade root coupled to the central hub; a distal portion including a blade tip; and a mid-portion disposed between the proximal portion and the distal portion; a first shroud having inner surface portions in proximity to the blade tip; and a hinged pitch mechanism configured to lengthen or shorten a distance between at least some of the inner surface portions of the first shroud and the central axis.
 15. The shrouded fluid turbine of claim 14, further comprising an ejector shroud located downstream from the first shroud; wherein the first shroud comprises mixing lobes.
 16. The shrouded fluid turbine of claim 14, further comprising a control mechanism to control the positions of at least some of the inner surface portions relative to the central axis.
 17. The shrouded fluid turbine of claim 16, wherein the control mechanism individually controls the position of each inner surface portion for a plurality of the inner surface portions. 18-22. (canceled)
 23. An energy extraction shrouded fluid turbine comprising: a rotor having a central hub rotatable about a central axis of the energy extraction shrouded fluid turbine; a blade having: a proximal portion including a blade root coupled to the central hub; a distal portion including a blade tip; and a mid-portion disposed between the proximal portion and the distal portion; a first shroud having: an inner surface in proximity to the blade tip; and mixing lobes; and an adjustment mechanism configured to change a distance between the blade tip and the shroud inner surface by lengthening or shortening a distance between at least a portion of the shroud inner surface and the central axis.
 24. The energy extraction shrouded fluid turbine of claim 23, further comprising an ejector shroud located downstream from the first shroud.
 25. The energy extraction shrouded fluid turbine of claim 23, wherein the adjustment mechanism comprises an inflatable bladder coupled with the shroud inner surface and configured to change a distance between at least a portion of the shroud inner surface and the central axis upon inflation or upon deflation of at least a portion of the inflatable bladder.
 26. The energy extraction shrouded fluid turbine of claim 23, wherein the adjustment mechanism comprises a hinged pitch mechanism. 27.-39. (canceled)
 40. A method of adjusting a blade tip-shroud gap spacing in an energy extraction shrouded fluid turbine including a central hub rotatable about a central axis of the energy extraction shrouded fluid turbine, a blade having a blade tip, and a first shroud having an inner surface in proximity to the blade tip, the method comprising: sensing a spacing between the blade tip and at least a portion of the inner surface of the first shroud during rotation of the blade about the central axis; and changing a distance between the blade tip and the central hub in response to the sensed spacing.
 41. The method of claim 40, wherein the energy extraction shrouded fluid turbine further includes an ejector shroud; and wherein the first shroud has mixing lobes.
 42. The method of claim 40, wherein sensing the spacing between the blade tip and the shroud inner surface comprises detecting a radial position of the blade tip relative to the central axis or relative to the shroud inner surface.
 43. The method of claim 40, wherein sensing the spacing between the blade tip and the shroud inner surface comprises optically detecting a position of the blade tip relative to the central axis or relative to the shroud inner surface.
 44. The method of claim 40, wherein changing a distance between the blade tip and the central hub comprises changing the distance between the blade tip and the central hub in real time during operation of the shrouded fluid turbine.
 45. The method of claim 40, wherein changing a distance between the blade tip and the central hub comprises extending or retracting at least a portion of the blade with respect to the central hub.
 46. The method of claim 40, wherein the at least a portion of the blade is extended or retracted telescopically.
 47. The method of claim 40, wherein changing a distance between the blade tip and the central hub comprises displacing at least the blade tip and the blade mid-portion in a radial direction with respect to the central hub.
 48. The method of claim 40, wherein changing a distance between the blade tip and the central hub comprises rotating at least the distal portion of the blade relative to the proximal portion of the blade about a non-radial axis.
 49. The method of claim 40, wherein changing a distance between the blade tip and the central hub comprises rotating at least the distal portion of the blade relative to the central hub about a non-radial axis.
 50. A method of controlling a blade tip-shroud gap spacing in an energy extraction shrouded fluid turbine including a central hub rotatable about a central axis of the energy extraction shrouded fluid turbine, a blade having a blade tip, and a first shroud having an inner surface in proximity to the blade tip, the method comprising: detecting a spacing between the blade tip and at least a portion of the shroud inner surface during rotation of the blade about the central axis; and actively controlling a distance between the blade tip and the central hub during rotation of the blade based on the detected spacing.
 51. The method of claim 50, wherein actively controlling a distance between the blade tip and the central hub during rotation of the blade comprises changing the distance between the blade tip and the central hub in real time during operation of the shrouded fluid turbine.
 52. A method of adjusting a blade tip-shroud gap spacing in an energy extraction shrouded fluid turbine including a central hub rotatable about a central axis of the energy extraction shrouded fluid turbine, a blade having a blade tip, and a first shroud having an inner surface in proximity to the blade tip, the method comprising: sensing a spacing between the blade tip and at least a portion of the inner surface of the first shroud during rotation of the blade about the central axis; and changing a distance between at least a portion of the shroud inner surface and the central axis based on the sensed spacing.
 53. The method of claims 52, wherein the first shroud has mixing lobes, and wherein the energy extraction shrouded fluid turbine further includes an ejector shroud downstream of the first shroud.
 54. The method of claim 52, wherein changing a distance between at least a portion of the shroud inner surface and the central axis based on the detected spacing occurs during operation of the energy extraction shrouded fluid turbine and during rotation of the blade.
 55. The method of claim 52, wherein the energy extraction shrouded fluid turbine further includes an inflatable bladder associated with the shroud inner surface, and wherein changing a distance between at least a portion of the shroud inner surface and the central axis comprises inflating or deflating at least a portion of the inflatable bladder.
 56. The method of claim 52, wherein the energy extraction shrouded fluid turbine further includes a hinged pitch mechanism, and wherein the distance between the at least a portion of the shroud inner surface and the central axis is changed using the hinged pitch mechanism. 57.-61. (canceled) 